The present invention relates to a visual inspection apparatus using a scanning electron microscope (SEM), a review apparatus, and an alignment coordinate setting method for use in defect coordinate alignment, which are applied to steps of manufacturing a semiconductor device to observe a defective part in a semiconductor sample detected by the SEM visual inspection apparatus with use of the review apparatus with a high resolution.
A semiconductor device is formed after a semiconductor sample undergoes a plurality of steps of oxidization, film deposition, light exposure, etching, etc. The semiconductor sample is inspected as necessary in the midway of the plurality of steps with use of an inspection apparatus such as a foreign matter inspection apparatus or a visual inspection apparatus. And coordinate information about a foreign matter or visually defective part in the semiconductor sample is transmitted to a review apparatus via a network or the like for high-resolution observation.
A SEM visual inspection apparatus, which is a scanning electron microscope (SEM) for scanning an electron beam across a semiconductor sample applied to an inspection apparatus, is featured by detecting an electrical defect such as a contact failure in a hole step, disconnection or short-circuiting in a wiring step, which could not be detected by an optical inspection apparatus. In the SEM visual inspection apparatus, patterns on the semiconductor sample to be inspected are irradiated with an electron beam, secondary electrons emitted in response to various materials of the patterns are detected, the amount of detected secondary electrons is converted to gray scale to thereby form an image, the formed image is stored in an image processing memory in the apparatus, patterns repeated at intervals of several microns in the chip or patterns at the same locations of adjacent chips are mutually compared with the stored image, and the location where a difference of the patterns is found is extracted as a defective part. In the SEM visual inspection apparatus including an optical microscope, rough alignment of the semiconductor sample is carried out using the optical microscope, while fine alignment is carried out based on the SEM image.
After completing the inspection, the apparatus expressed coordinate information on the detected defective part by a chip layout number and an in-chip coordinate, and then transmits the coordinate information as an inspected result, together with chip layout information and semiconductor sample alignment information relating to the semiconductor sample and prepared using an inspection recipe, to the review apparatus via a network or the like.
The review apparatus, on the basis of the inspected result received from the SEM visual inspection apparatus, displays a chip layout of the semiconductor sample to be observed and a coordinate map of the defective part detected by the visual inspection apparatus, and prepares a defect coordinate list. A defect coordinate includes the layout number of the chip containing the defect in the semiconductor sample and an ordinate in the chip. In the review apparatus, the relative coordinate of the defect present in the semiconductor sample and detected by the SEM visual inspection apparatus is set at the time point that the review apparatus reads the inspected result received from the SEM visual inspection apparatus. However, the defect present in the semiconductor sample cannot be observed only by setting the relative coordinate of the defect present in the semiconductor sample. This means that a distance was set between a defect detected at a position and a defect detected at another position. When coordinate alignment is not conducted between the SEM visual inspection apparatus and the review apparatus, however, the review apparatus cannot move its stage to the coordinate of the defect in the semiconductor sample detected by the SEM visual inspection apparatus. To realize this, the coordinate alignment information on the semiconductor sample is transmitted from the SEM visual inspection apparatus to the review apparatus, which in turn moves the stage to the target coordinate of the defect on the basis of the coordinate alignment information.
In the first processing step of the alignment of the review apparatus, the review apparatus refers to the inspected result received from the SEM visual inspection apparatus, and moves the stage to the alignment coordinate specified in the SEM image by the SEM visual inspection apparatus under automatic control. However, due to a difference in the amount of rotation of the semiconductor sample fixed in each sample holders or a difference in the set center coordinates between the SEM visual inspection apparatus and the review apparatus, the review apparatus cannot move the stage to the alignment point in the SEM image specified by the SEM apparatus with a high possibility. In the review apparatus, further, since searching for the first alignment point is carried out based on the optical microscope image, it is difficult to identify the alignment point specified in the SEM image. For such a reason, when the review apparatus do the alignment, without an instruction from the operator of the SEM visual inspection apparatus or without data indicative of the alignment point specified by the SEM visual inspection apparatus, a working efficiency drops.
There is known an apparatus in which a visually-recognizable mark is made on a semiconductor sample by ink jet, laser machining or sputtering (e.g., refer to JP-A-2000-232138) or a system in which a mark is made by an electron beam in the vicinity of a defect in a semiconductor sample (e.g., refer to JP-A-2001-127125 corresponding to U.S. Pat. No. 6,566,654).
Further, even when the same operator operates the SEM visual inspection apparatus and the review apparatus, the operator may erroneously specify an alignment point from his misunderstanding. Thus there may occur such a situation that the operator cannot move the stage to the coordinate of the defect detected by the SEM visual inspection apparatus. In this case, the operator is required to again load the sample in the SEM visual inspection apparatus to confirm the alignment point.
In the above prior art, when the defect in the semiconductor sample detected by the SEM visual inspection apparatus is observed using the review apparatus with a high resolution, information transmission of the coordinate alignment of the detected defect, so called alignment point specification has been conducted frequently manually. For this reason, the inspection system in semiconductor manufacturing steps had a low working efficiency and a low reliability.